Day 12 - Bond Dissociation Energy and Resonance

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Rhode Island Department of Education
Lesson Plan
Lesson Title: Bond Dissociation Energy and Resonance

State Standards: (GLEs/GSEs)
GSE - PS1 (9-11) - 4

National Standards:


Context of Lesson:
This lesson is after the class has done the strength of covalent bonds activity/lab in class. In that lab the students learned that triple bonds are stronger than double bonds which are stronger than single bonds. This class will focus on why knowing this is important. I will introduce bond dissociation energy to the class and relate it to the strength of bonds. I will also touch upon resonance which can also effect the bond dissociation energy.

Opportunities to Learn:
Depth of Knowledge:
  • Level 2
    • Describe how oxygen atoms are bonded in ozone.
    • Organize 3 compounds in order of increasing bond strength.
    • Organize 3 compounds in order of decreasing bond dissociation energy.

Prerequisite Knowledge:
  • Periodic Table
  • Covalent bonds
  • Bond Strength

Plans for Differentiating Instruction:
This class will have mostly a lecture; however, the students will be hearing and seeing the information in various ways so that all the different types of learners can see the information in a way that they understand.

Accommodations and modifications:
I could give some students a list of bond dissociation energies. Also, I could give students 2 compounds instead of 3 compounds when they have to organize them in order of bond strength and bond dissociation energy.

Environmental factors:
The students will be sitting in their normal groups.

Materials:

Objectives:
  • When given 3 compounds the students will organize them in order of decreasing bond dissociation energy.
  • Students will describe how oxygen atoms are bonded in ozone.
  • When given 3 compounds the students will organize them in order of increasing bond strength.

Instruction:
Opening:
  • Talk about the lab from the day before.
    • Did the students see any trends in the lab?
      • Do they think there is any significance in the trends?

Engagement:
  • Bond dissociation energy.
    • What do you think this means?
      • Think about the lab and the trends we were just talking about...
      • Lead the students to define the word on their own and make the connections to the lab.
        • Its harder to break 3 rubber bands than 1 rubber band.
          • Demonstrate.
          • A triple bond is stronger and harder to break so it needs more energy to break it.
  • Why is it significant that it takes more energy to break a triple bond than a single bond?
    • What properties could that effect?
      • Melting and boiling points.
        • More bonds to break
  • Do you think there are other things that can effect the bond dissociation energy?
    • Expect to hear “yes” because I asked the question.
    • There are other things that can effect bond strengths.
      • Resonance.
        • Powerpoint.
        • What is it?
          • Difficult to understand.
          • The electrons can move in order to stabilize a compound
            • Example: Ozone (O3)
        • It contributes to some exceptions to the octet rule.
          • As we already know chemistry is complicated and some rules can be broken.
          • Compounds with an odd number of valence electrons do not follow the octet rule and therefore have resonance.

Closure:
  • Review the trends that the students saw with bond dissociation energies.
  • Remind the students that the lab is due in the next class.

Assessment:
The assessment for this class will be done through questioning and will be on the final unit test.

Reflections:
(only done after lesson is enacted)


Student Work Sample 1 – Approaching Proficiency:

Student Work Sample 2 – Proficient:

Student Work Sample 3 – Exceeds Proficiency: